The present invention relates generally to mufflers, and particularly to a discharge muffler for attenuating the sound resulting from the pressure pulses in the discharge of a gas compressor, such as a hermetic refrigeration compressor.
Unlike many exhaust mufflers, the mufflers required for use on hermetic compressors must meet a number of relatively complex and sometimes conflicting objectives. The most difficult objectives to meet concern the achievement of a reasonable level of sound attenuation without a significant decrease in performance. In a refrigeration compressor system it is the muffled gas which performs the work of the system, and to maintain a high level of overall efficiency and the necessary mass flow in the system the muffler must impose a minimum pressure drop in the gas flow therethrough. The difficulty lies in the fact that generally speaking the greater the degree of sound attenuation achieved by a muffler the greater the performance loss, and vice versa. Other design objectives include compactness, cost, ease of mass production, ease of assembly, reliability, and the like.
Many of the mufflers used on hermetic refrigeration compressors are variations of a "bandpass filter," one of which is a well-known muffler concept wherein two substantially equal volume chambers are joined by a tube having a length approximating the length of each chamber. The muffler of the present invention is a further improved variation of this type of sound attenuation device.
Considering the most relevant prior art of which applicant is aware, Nordquest U.S. Pat. No. 3,220,508 discloses a sheet metal multi-chamber automotive muffler wherein the baffles are retained by ridges in the muffler sides, and wherein a tube interconnects the chambers and has a restriction therein. Hald U.S. Pat. No. 3,171,506 discloses a sheet metal muffler construction for a refrigeration compressor which is formed from a plurality of "U" shaped members which are joined together to form a multi-chamber muffler. Communication between the chambers is provided by a tube extending through adjacent walls of separate "U" shaped members. Kleinlein U.S. Pat. No. 3,279,683 discloses a sheet metal muffler for a refrigeration compressor comprising an inlet tube with a restricted end portion extending through a first chamber and baffle and opening into a second chamber. The compressed gas then passes through an aperture provided in the baffle into the first chamber and out an exhaust passage communicating therewith. Gleason U.S. Pat. No. 3,458,121 discloses a multi-chamber cast muffler construction for a refrigeration compressor having a tube extending through a central baffle, and an outlet tube having an annular restriction therein. Although these prior mufflers may be satisfactory for certain of the applications for which they were designed, it is believed that the muffler of the present invention provides superior overall performance for the total cost involved.
The primary object of the present invention is thus to provide an improved discharge muffler construction which provides the required degree of sound attenuation without a significant loss of performance, and in a relatively inexpensive, compact construction which functions reliably for the life of the compressor on which it is mounted.
These and other objects, features and advantages of the present invention will become apparent from the subsequent description and the appended claims, taken in conjunction with the accompanying drawings.